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Show The predicted product distribution appears in Figs. 5b and c plotted versus the instantaneous particle temperature. Devolatilization begins at 750 K for this heating rate and is completed in 15 ms when the particle temperature has reached about 1500 K. Tar is the first and predominant product, as expected for this hvA bituminous coal. The ultimate tar yield of 43 daf wt. % comprises three-fourths of the ultimate weight loss of 57 wt. %. Noncondensible gases are split evenly among hydrocarbons and the 3 oxygenated gases, whose yields appear in Fig. 5b in ascending order for CO2, (chemically formed) H20, and CO. The nitrogen species distribution in Fig. 5c shows that tar is clearly the major shuttle for fuel nitrogen from this coal (and all other types). The amount of HCN directly released is very small, although secondary volatiles pyrolysis would, in actuality, convert about two-thirds of the tar-N into HCN in the hot entrainment gas for this simulation. Additional HCN would also be expelled from the char on much slower time scales, although this is not likely to be an important mechanism in pulverized coal flames. The char retains 44 % of the fuel-N, which is nearly equal to the char mass fraction on the dry-ash-free basis. These fractions are consistent because tar shuttles away fuel-N at the same relative concentration as in the original coal, and all other mechanisms of fuel-N release are unimportant during the initial stages of rapid coal devolatilization. REFERENCES 1. Niksa, S., Energy Fuels 8:659 (1994). 2. Niksa, S., Energy Fuels 8:671 (1994). 3. Niksa, S., Energy Fuels 9:467 (1995). 4. Fletcher, T. H., Kerstein, A. R., Pugmire, R J., Solum, MS., and Grant, D. M., Energy Fuels 6:414 (1992). 5. Solomon, P. R., Hamblen, D. G., Serio; M. A., Yu, Z.-Z., and Charpenay, S., Fuel 72: 469 (1993). 6. Niksa, S., Combust. Flame 100:384 (1995). 7. Niksa, S., Twenty-Fifth Symposium (International) on Combustion, The Combustion Institute, 1994, p. 537. 8. Chen, J. C. and Niksa, S. Energy Fuels 6:254 (1992). 9 |